Process for treating acid sludges



JUIY 25, 1933- D. R. MERRILL Er AL I 1,919,664

PROCESS FOR TREATING ACID SLUDGES Filed Jan. 28, 1929 4. Conce/7 fra/lor) I l/ff @120W/MM ATTORNEY.

l A` further 'objection resides in the fact that sludges produced in the sulfuric acidtreat- Patented July 25, i933 UNITED "STATES PATENT-'OFFICE DAVID R. MERRILL, OE LONG BEACH, AND PHILIP `s.. CLARKEOE BERKELEY, CALI- FORNIA, AssIGNORs To UNION OILCOMIANY or CALIFORNIA, OE Los ANGELES, CALIFORNIA, A CORPORATION OE CALIFORNIA i l v Application filed January 28, 1929. Serial No.i,335,6 2t5.

T'his invention relates to methods .for the separation and recovery of sulfuricl acidffrom acid sludges so that the acid may be comentrated for further use and the tarry portions of the sludges may be employed asfuel.

Acid sludgeA obtained from thetre'atment ofvariouspetroleum oils'consists of alarge vportion of sulfuric c acid infin'timate '.adinix ture'vvith various organic compounds such as' too 'low a purity to permit concentration for re-use because *of the presence of excessive quantities of carbonaceous impurites which cause the decomposition of excessivequanti tics of sulfuric acid during concentration;

mentiof light oils such as gasoline; kerosene, and engine distillates obtained from petrole-y um oils particularly asphaltic base orCalifornia crudes, emulsify spontaneously-with Water; this is a decided difference fromthe action `of lubricating oil *acid sludges which do not so emulsify. Due to such ready emul- Q.silication of'light oil sludges of vtheabove characterseparatioii of the acid from the tar-V ry constituents cannot be made satisfactorily by those Washing processes which have been usedfor `heavy oil sludges. AIt hastherefore been the practice to run the light oil sludgesl to Wastaor to burn them While still contaiirs ing` large amounts of sulfuric acid, a procedurel involving both nuisance and Waste.

It isthe objectof our invention to present a process whereby light oil sludges may be satisfactorily treatedvfor the economical re.. coveryofv the'sulphuric acid'from the tarry portions and torender such tarry portions available for fuel. i'

We have discovered that tlieemulsiable light oil acid sludges obtained from petroleum oils, such as light oil sludges from asphaltic baseand California crudos, can be" prevented from emulsifying byl Washing such light oil sludges with a'liquor which already `ily handled.

contains a comparatively high percentage of sulfuric acid. f We have also discovered that the emulsilication of light oilsludges may; be prevented by -vvashing themin admixture with relatively'large quantitiesvof heavy oil sludges, for example lubricating oil sludges7 content of thesludges be low.V In thel first -Y instance those organic compounds Which are Waterfsolulole` and cause the emulsiiicationl are prevented from dissolving in the aqueous phase `by the high sulfuric acid content of the patible in the` same solution. lnthose cases lWherev the'lieavy and lighto-il sludges'nave Vbeen previously Washed `(With strong acid; liquor, `for example);'suchjwashed sludges will be miXedbefOi-evbeing given' a second Wash to remove the `greater portion ofthe residual acid. Thereason for mixing these ith/eilig then unnecessary lthat thevvash'xvan v ter initially contain acid even thoughthe acid Y .samenan effectapparentanalogous to saltonce-washed sludges is that the heavyOil sludge vserves lto stituents of the light oil sludge to such eX'- tent that said constituents become 'inopera tive. For proportion of heavy oil sludge must be used; Three times as much heavy oil sludge as light oil sludge usually is req ired, and a greater quantity may be employed if desired.A The ratio of three-to-One is typical, but sludges ocdilute the emulsifying coni this purpose a comparatively large casionally are found Whereajtuf'oto-One orV one-tofone ratio Will meettherequirements. `Not only does the heavy o il sludge effect dilu tion of the light oil sludge to preventemulsiiication of the latter, buttheliglit oil sludge also acts to reduce the viscosity of `the heavy` Oil sludge in order that it may be more'read-z/ ell le have found a convenient method of operation to reside in What may be termed a counter-current7 Washing method, that is, Washing a previously Washed sludge or mixture of sludges of low acid content With Water containing little or no acid, and using the resulting Wash liquor to. Wash fresh batches of sludges of high acid content. rllhis Washing method is preferably, Worked out in order to treat the light oil sludges with the strongest possible Wash liquor, and this may be accomplished with a counter-current process comprising Washing 'a mixture of previously Washed light oil and lubricating (heavy)V oil sludges with water containing little or no acid, using the resulting Wash liquor to Wash a fresh lubricating (heavy) oil sludge, and then employing the resultin'g comparatively strong acid Wash liquor to wash a fresh batch of light oil"sludge,`` The liquor from the last mentioned wash may then be further treated to separate asmuch of its tai-ry content as possible, and subsequently concentrated. l

Therefore, broadly stated, the invention resides in treating a lightoil acid sludge to prevent emulsification thereof by admixing said light oil sludge with a large proportion (as above defined) of a heavy (lubricating) oil sludge and Washing the mixture with \vater.

rllhe invention resin-es also in Washing a light oil acid sludge with a strong acid liquor, preferably a liquor obtained from Washing a. heavy'oil sludge. The invention also resides in the purification o'f'liquois from the two types of sludges by heating a mixture of, such liquors to cause impurities to separate. The invention resides further in combining these steps to obtain a highly acid liquor for final purification, and to obtain a lsludge r s` idue as free as possible from acid, and suitable for use as fuel. In operating this com-` bination of steps according to a desirable form, previously Washed heavy and light oil sludges are mixed together and then Washed with fresh Water preferably regulated in amount to produce a liquor of minimum density compatible with its causing the` tarry material to float on it thus facilitatingthe mechanical operation of separating thetar andsaqueous phases, employing such resulting liquor to Wash a fresh batch of heavy acidu sludge to procuce a resultant Wash liquor having a comparatively high acid con-I tent, and in turn employing theresultant strong liquor to Wash a fresh batch of light oil sludge, the highly acid liquor from which may be further purified and concentrated. These once-Washed vacid sludges are vthen mixed and Washed With freshwater as above indicated to commence a new cycle.

In the accompanying drawing a preferred method of operating the present inventionis diagrammatically indicated, ln this instance, an agitator A contains a heavy acid sludge such as lubricating oil sludge to be treated, and an agitator A contains a light oil acid sludge such as kerosene or gasoline sludge to be treated, the light oil sludge being one :Which Would emulsifyif treated With fresh Water. A kettle l is employed to receive heavy oil acid sludge from the agitator and a kettle 2 is employed to receive a .Washed or treated sludgeV from kettle l.

v A third kettle 3 receives charges of light oil l'lgSQi, but the concentration of this acid in the sludge on a tar-free basis is much higher,

varying from 50 to 75% in most cases. The

lash is accomplished by heating the mixture of sludge and acid liquor with open or closed steam coils, preferably open coils in order that the mixture may be agitated by the steam, carrying a temperature of around 240 to 260 F; and continuing such treatment for a time suflicient to accomplishl satishv factory separation of the acid liquor from the tarry constituents. The temperature einployed is sufficient to boil the solution and. the time to accomplish the desired results may vary from 15 or 20 minutes to 'one or tivo hours, according to the materials being handled. n n

The strong Wash liquor obtained from ket tlel and containing approximately 40% HZSO, and from 0.5% to 10% or Carbon based on the Weight of the acid in the liquor, is nov] employed to Wash a fresh batch of light oil sludge `introduced into thekettle 3 froml the agitator A", such light oill sludge normally having an acidity of about H2301. The mixture o f strong acid liquor and fresh light oil sludge in kettle 3 is given a treatment preferably with steam from open coils, similar to the treatment carried on inv kettle 1, the temperature being maintained at about 240 to 260O F. in order to boil the solution and obtain good contact, and the time being sufficient to obtain'a satisfactory separation of the emulsified tarry constituents from the sulfuric acid solution. In this instance also the time of treatment Will vary from l5 to 20 minutes to one or tivo hours according as the materials treated vary. The cooking in the kettle 3 is sufficient to purify partially the resultant sulfuric acid liquor so that substantially all of the sludge separates out. The completeness of the treatment and of the separating operation is indicated by the formation of a clear, light-colored solution when isc a a sample of the separated acid liquor is poured into a large volume of Water. Should a turbid solution develop it Will be indicative of the necesssity for longer treatment. The resultant separated sulfuricy acid solution should have an acidity of over H2SO4 and may run as high as H2SO4 Land will have a carbon content of from 0.5 to 4% based on the acid content.

The partially purified strongsulfuric acid liquor so obtained in kettle 3 after a short period of settling is run into kettle 4 Where it is boiled with closed steam coils at a temperaturefrom 260 to 320O F. for the purpose of converting the organic impurities in the acid into insoluble vforms by the combinedV effect of the acid and the high temperature, so that being insoluble they Will separate and rise to the surface. This re-cooking operation is carried on for a time suicient to accomplish the desired results as stated which ordinarily requires from three to live hours.

The finished sulfuric acid liquor resulting from the cooking in the kettle 4 is then conducted to a concentration plant 5 Where it is prepared for reuse.

Small amounts of tar and other insolubles separated in the kettle 4, together with the once-Washed light oil sludge from theI kettle 3, are conducted into the second Wash kettle 2 Where they are `mixed with the once-Washed lubricating oil sludge from the kettle1.

This mixture of the heavy and light oil sludges is then treated With steam, preferably from open coils, at a temperature and for a time similar to the treat-ing conditions maintained in kettle 1, in the presence of fresh Water added in an amountcarefully controlled so as to yield an acid liquor of suflicient density to float the Washed sludge and thus facilitate mechanical separation. This Will ordinarily require an acidity in the acid liquor of about 20%. Since the sludge mixture contained in kettle 2 has an acid content of about 10% HZSO4 on a basis which i carbon based on the acid content.

The'tWice-Washed sludge discharged from kettle 2 is now in a condition for use as fuel, and normally contains less than 2% of sulfuric acid. Y

The above procedurel mav be variously modified Within the scope of the invention as regards the choice of Washing media and methods of purification of the acid liquor.

For example'the fresh'lubricating oil sludge may be `Washed With freshwater. This results frequently in the production of an acid vliquor of low purity, but purification can be dispersion characteristics and separating in insoluble form. Also When cooking light oil acid sludges, Water may be used asa diluent but itis necessary to maintain lthe strength of the sulfuric acidV in the mixture at a relatively high concentration in order to separate the tarry matters from the acid constituents satisfactorily. The best results have been ob- 'tainedy WhenV the strength of the acid in said vmixture runs between 50 and 65%` H2504.

Acid liquor separated in this fashion from light oil acid sludges may be purified by treatment in admixture With lubricating oil acid sludge or With acid liquor derived from'such sludge, the treatment being carried on under troduced into. the twice-Washed sludge taken y off for fuel. These skimmings are obtained from the Waste alkali liquor drawn from vthe agitators A, Aatother stages of treatment of the oil stocks, the skimmingsbeing a lmixture of oil and naphthenic and other organic acids precipitated ina neutralizing box 6 by acidification of saidvvaste alkali liquor with some acid Wash liquor4 diverted at any convenientjpoint in the Washing operations, for example from -.the line leading from kettle 1 or the line leading from kettle2. In this manner the recovery of said neutral skimmings. is conveniently accomplished.

The above descriptions aremerelv'illustrative ofthe generic invention` and it is to be understood that many modifications may be made Within the range of the accompanying claims by those skilled in the art.

We claim:

1. A method for treating acid sludges'comprising'washing a heavy oil sludge with a Weakacid Wash liquor, employing the resultant strong acidWash liquor to Wash a light oil sludge Which femulsifies When Washed with fresh Water, mixing the Washed heavy and light oil sludges, Washing such mixed sludges Withfresh Water. and employing the-resultant Weak Wash liquor as the washing medium fora fresh batch of heavy oil sludge in anew cycle.

2. A method for treating acid sludges V- comprising mixing previously` Washed light and heavy oil sludges, Washing such mixture with water, employing the resultant acid liquor to Wash a fresh heavy oil sludge, and employing a strong acid liquor from the last mentioned Wash to wash a fresh batch of light oil sludges.

3. A method according to claim 2 wherein the strong acid liquor from the wash of the fresh light oil sludge is heated until impurities separate out, and recovering the resultant puriiied acid liquor.

4a A method for recovering acid from acid sludges obtained from the treatment of petroleum products, comprising mixing a heavy oil sludge with a light oil sludge7 the light oil sludge being such that it would tend to emulsify if washed alone with fresh waterwash ing the sludge mixture with water at a temperature sufficientl to boil the solution to cause separation of tarrv constituents and washing a fresh batch of heavy oil sludge rwith the acid liquor from the first mentioned wash at a temperature suiiicient to boil the solution for the separation of tarry constituents.

5. A method for recovering acid from acid sludges comprising washing a heavy oil sludge with a weak acid wash liquor at an elevated temperature to cause separation of tarry constituents from the resultant liquor7 employing the resultant strong acid liquor to Wash a light oil sludge which emulsiiies when washed with fresh water, the washing of said light oil sludge with the strongacidy liquor being carried on at a temperature to boil the solution and cause separation of tai-ry constituents. mixing` the Washed heavy and light oil sludges, Washing such mixed sludges with fresh water, and employing the resultant weak wash liquor as a washing medium for a batch of heavy oil sludge in a new cycle.

6. A method for the separation of the constituents of acid sludges obtained from acid treatment of petroleum products, comprising washing a heavy oil sludge with a weak acid liquor at a temperature to boil the solution, employing the resultant strong acid liquor to Wash a light oil sludge which would emulsify if washed with fresh water, the washing of the light oil sludge With the strong acid liquor beingcarriedr on at a temperature to boil the solution for the separation of tarry constituents, and heating the strong liquor' from the washing of the light oil sludge at a temperature to boil the solution to separate impurities in insoluble form.

7. A method for recovering acid from acid sludges comprising washing a heavy oil sludge and obtaining a strong acid liquor therefrom, washing a light oil sludge with said acid liquor, the light oil sludge being` inclined to emulsify if Washed with fresh water, continuing the Washing of the light oil sludge With said liquor at an elevated temperature to cause separation of the tarry constituents, and heating the strong acid liquor from the wash of the light oil sludgeto cause separation of impurities.

8. A method according to claim 7 wherein the wash-ed heavy and light oil sludges are mixed and washed with water, and the resultant liquor is employed to wash the heavy oil sludge in a new cycle.

9. A method for recovering acid from acid sludges comprising treating with a strong acid wash liquor a. light oil sludge having a tendency to emulsify when washed with fresh water, heating the solution during such treatment with acid liquor to cause separation of tarry constituents, and heating the acid liquor resulting from such treatment in admixture with acid liquor from the treatment of heavy oil sludges to cause separation of impurities from the mixed liquors.

l0. A method for recovering acid from light oil sludges which tend to emulsify when treated with fresh water, comprising treating said sludges with a wash liquor suiliciently strong in acid to prevent emulsiiication, and heating the mixture at an elevated temperature to cause separation of tarry constituents from the liquor. Y

li. A method -for recovering acid from light oil sludges which emulsify when treated with fresh water, comprising boiling the light oil sludge with a wash liquor containing acid sufficient to prevent emulsiiication,` and continuing the boiling for separation of tarry constituents until a clear light-colored solution will form when a sample of the separated acid liquor is poured into a large volume of water.

l2. A method of treating acid sludges which comprises mixing an acid sludge which emulsifies when washed with water with anV acid sludge which will not emulsify when washed with water and washing the mixture with water.

13. A method for treating acid sludges comprising mixing an acid sludge which emulsiiies when washed with water with an acid sludge which will not emulsify when washed with water7 washing the mixture with water, and washing a fresh batch of nonemulsifying sludge with the acid liquor from the washing of the sludge mixture.

14. A method for treating acid sludges com` prising employing a liquor to wash a mixture of previously washedsludges which respectively are emulsifying and non-emulsifying when Washed with water, then washing a fresh batch of non-emulsifying sludge with the resulting liquor from said previous wash and then washing a fresh batch of emulsifying sludge with the resulting liquor from said wash of the non-emulsifying sludge.

15. A method for treating acid sludges comprising employing a liquor to Wash a mixture of previously washed sludges which respectively are emulsifying and non-emulsifying when washed with water,` then wash- Cil ing a fresh batch of non-emulsifying sludge With the resulting liquor from said previous Wash, then Washing a fresh batch of emulsifying sludge With the resulting liquorl from said Wash of the non-emulsifying sludge and boiling the resultant liquor to separate impurities therefrom. i

16. A method for treating acid sludges from petroleum treating processes comprising mixing previously Washed acid sludges in the proportion of at least one part of an oil sludge which Will not emulsify when Washed with Waterto one part of an oil sludge Which emulsiiies when washed with Water and heating such mixture With Water containing substantially no acid to ohtain a separation of acid liquor from the mixed sludges. i

17. A method for treating oil sludges which emulsify when Washed with Water and oil sludges Which will not emulsify When Washed With Water comprising Washing a mixture of such sludges and heating the liquor from said Wash to cause the separation of impurities.

.-18. A` method for treating oil sludges VWhich emulsify When Washed with Water and 'oil sludges which Will not emulsify When Washed With Water comprising Washing a y mixture of such sludges at a temperature approximately 24() to 260 F., vand heating the liquor from said Wash to cause the separa' .tion of impurities. 

